China makes breakthrough in 'invisible' materials

According to SCMP , Chinese researchers have developed a material that can change color at the molecular level based on ambient light , creating a new form of camouflage that helps people blend into their environment like a chameleon.

"In other words, applying this technology to clothing can make us 'invisible' ," said project leader Wang Dongsheng at the University of Electronic Science and Technology of China.

China's invisible painter blends into the environment. Scientists in the country are developing a material that can change color without having to be colored first. (Photo: Baidu).

In research published last month in the journal Science Advances, Wang's team said they aimed to make active camouflage "instinctive" in color-switching materials, in a process they call self-adaptive photochromism (SAP).

The key to this transformation is a molecular compound that changes structure when exposed to specific wavelengths of light. To the naked eye, the material appears to blend perfectly into its surroundings.

In nature, both chameleons and octopuses rely on active camouflage, changing their appearance to blend into their environment. Artificial systems typically achieve this effect through complex electronics, resulting in high costs and limited availability.

In contrast, SAP technology offers a simpler and more efficient method of achieving adaptive camouflage effects, without the need for external power sources or complex electronics.

To demonstrate, the researchers placed a transparent container containing SAP solution into opaque acrylic boxes of different colors — red, green, and yellow, with black ink as a control — and observed the solution change color accordingly.

In another experiment, the report said, within 30 to 80 seconds, the container could blend into its surroundings when placed in a matching colored environment, such as a cluster of red, green, or yellow plants.

The technology can also be applied as a coating. By incorporating polycaprolactone (PCL) , the researchers have developed SAP films and coatings that can be sprayed or applied to a variety of surfaces, allowing for adaptive camouflage on solid materials.

According to the study, the ability of SAP material to rapidly change color opens up exciting new prospects in areas such as camouflage, encryption, as well as stealth technology.

SAPs have great potential in camouflage systems, smart coatings, and fashion design, Wang notes in the research paper. In addition, because these materials work effectively in a temperature range of -20 to 70 degrees Celsius, they are also suitable for military and architectural applications.

The next phase of research will be based on the properties of SAP materials, Mr. Wang added.

'We haven't fully reproduced all the colors in the visible light spectrum in this work. That will be done in future studies,' he says. Purple and blue are not currently available in the SAP material, but future improvements could address that.

'By adding more photochromic molecules or adjusting the composition of the material, we hope to achieve better color discrimination and faster change speed ,' said Wang.